ABSTRACT
Cafestol, a diterpene present in unfiltered coffee brews such as Scandinavian boiled, Turkish, and cafetière coffee, is the most potent cholesterol-elevating compound known in the human diet. Several genes involved in cholesterol homeostasis have previously been shown to be targets of cafestol, including cholesterol 7alpha-hydroxylase (CYP7A1), the rate-limiting enzyme in bile acid biosynthesis. We have examined the mechanism by which cafestol elevates serum lipid levels. Changes in several lipid parameters were observed in cafestol-treated APOE3Leiden mice, including a significant increase in serum triglyceride levels. Microarray analysis of these mice identified alterations in hepatic expression of genes involved in lipid metabolism and detoxification, many of which are regulated by the nuclear hormone receptors farnesoid X receptor (FXR) and pregnane X receptor (PXR). Further studies demonstrate that cafestol is an agonist ligand for FXR and PXR, and that cafestol down-regulates expression of the bile acid homeostatic genes CYP7A1, sterol 12alpha-hydroxylase, and Na(+)-taurocholate cotransporting polypeptide in the liver of wild-type but not FXR null mice. Cafestol did not affect genes known to be up-regulated by FXR in the liver of wild-type mice, but did increase expression of the positive FXR-target genes intestinal bile acid-binding protein and fibroblast growth factor 15 (FGF15) in the intestine. Because FGF15 has recently been shown to function in an enterohepatic regulatory pathway to repress liver expression of bile acid homeostatic genes, its direct induction in the gut may account for indirect effects of cafestol on liver gene expression. PXR-dependent gene regulation of cytochrome P450 3A11 and other targets by cafestol was also only seen in the intestine. Using a double FXR/PXR knockout mouse model, we found that both receptors contribute to the cafestol-dependent induction of intestinal FGF15 gene expression. In conclusion, cafestol acts as an agonist ligand for both FXR and PXR, and this may contribute to its impact on cholesterol homeostasis.
Subject(s)
DNA-Binding Proteins/agonists , Diterpenes/pharmacology , Receptors, Cytoplasmic and Nuclear/agonists , Receptors, Steroid/agonists , Transcription Factors/agonists , Animals , Apolipoprotein E3/genetics , Cholesterol 7-alpha-Hydroxylase/genetics , Coffee/chemistry , DNA-Binding Proteins/deficiency , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Diterpenes/adverse effects , Diterpenes/metabolism , Female , Fibroblast Growth Factors/genetics , Humans , Hypercholesterolemia/chemically induced , In Vitro Techniques , Ligands , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Models, Biological , Pregnane X Receptor , RNA, Messenger/genetics , RNA, Messenger/metabolism , Receptors, Cytoplasmic and Nuclear/deficiency , Receptors, Cytoplasmic and Nuclear/genetics , Receptors, Cytoplasmic and Nuclear/metabolism , Receptors, Steroid/deficiency , Receptors, Steroid/genetics , Receptors, Steroid/metabolism , Transcription Factors/deficiency , Transcription Factors/genetics , Transcription Factors/metabolism , Transcriptional Activation/drug effectsABSTRACT
The mechanisms of diet induced hyperlipidemia and atherosclerosis have been widely studied by delineating the role of candidate genes in transgenic and gene targeted mouse models. However, diet induced hyperlipidemia represents a complex process determined by many lipid genes that is only partly understood. This study is aimed at delineating the events induced by dietary intervention in different mouse models at the level of gene expression using microarray analysis. The focus is on the liver as the organ primarily responding to diet, and crucial in determining plasma lipid levels. Firstly, the effect of the genotype was studied. Expression profiles of liver genes were compared between APOE3Leiden (E3L), APOE knockout (E-/-) and C57BL/6JIco (B6) mice using the Incyte GEM 2.03 array carrying 9552 genes. Several hundred differentially expressed genes were identified indicating that the genotype alone effects gene expression. Secondly, the response of E3L mice to high-fat feeding was investigated using a mild and severe high-fat diet (diet W and N, respectively). Diet W caused differential regulation of 200 genes, while diet N affected the expression of 788 genes in B6 and 1010 genes in E3L mice. Annotation of these genes using the Gene Ontology (GO) database showed that two major processes were strongly affected by genotype and diet, namely lipid metabolism and inflammation, the latter as determined by "immune/defense response and detoxification" processes. Many nuclear receptor target genes were differentially regulated, with the largest effects modulated by the severe high-fat diet N, leading to the suppression of genes involved in bile acid, sterol, steroid, fatty acid, and detoxification metabolism. Strikingly, a substantial part of these nuclear receptor target genes were commonly regulated during the different experimental conditions. The common regulation of many nuclear receptor target genes underlying lipid and detoxification processes as found in this study, suggest a defense mechanism involving many nuclear receptors to protect against the accumulation of toxic endogenous lipids and bile acids. These results further strengthen the close link between hyperlipidemia and inflammatory processes.
Subject(s)
Atherosclerosis/genetics , Dietary Fats/pharmacology , Hyperlipidemias/genetics , Receptors, Cytoplasmic and Nuclear/genetics , Vasculitis/genetics , Animals , Apolipoprotein E3 , Apolipoproteins E/genetics , Atherosclerosis/immunology , Atherosclerosis/metabolism , Disease Models, Animal , Gene Expression Profiling , Gene Expression Regulation/immunology , Humans , Hyperlipidemias/immunology , Hyperlipidemias/metabolism , Liver/physiology , Mice , Mice, Inbred C57BL , Mice, Transgenic , Oligonucleotide Array Sequence Analysis , Receptors, Cytoplasmic and Nuclear/immunology , Receptors, Cytoplasmic and Nuclear/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Vasculitis/immunology , Vasculitis/metabolismABSTRACT
Myocardial right ventricular (RV) hypertrophy due to pulmonary hypertension is aimed at normalizing ventricular wall stress. Depending on the degree of pressure overload, RV hypertrophy may progress to a state of impaired contractile function and heart failure, but this cannot be discerned during the early stages of ventricular remodeling. We tested whether critical differences in gene expression profiles exist between ventricles before the ultimate development of either a compensated or decompensated hypertrophic phenotype. Both phenotypes were selectively induced in Wistar rats by a single subcutaneous injection of either a low or a high dose of the pyrrolizidine alkaloid monocrotaline (MCT). Spotted oligonucleotide microarrays were used to investigate pressure-dependent cardiac gene expression profiles at 2 wk after the MCT injections, between control rats and rats that would ultimately develop either compensated or decompensated hypertrophy. Clustering of significantly regulated genes revealed specific expression profiles for each group, although the degree of hypertrophy was still similar in both. The ventricles destined to progress to failure showed activation of pro-apoptotic pathways, particularly related to mitochondria, whereas the group developing compensated hypertrophy showed blocked pro-death effector signaling via p38-MAPK, through upregulation of MAPK phosphatase-1. In summary, we show that, already at an early time point, pivotal differences in gene expression exist between ventricles that will ultimately develop either a compensated or a decompensated phenotype, depending on the degree of pressure overload. These data reveal genes that may provide markers for the early prediction of clinical outcome as well as potential targets for early intervention.